1. Field of the Invention
The present invention relates to a solid-state imaging apparatus and more particularly to a solid-state imaging apparatus including an A/D conversion circuit in each column of pixels in a matrix to perform arithmetic processing to an obtained plurality of digital signals, and relates to a driving method of the solid-state imaging apparatus.
2. Description of the Related Art
In a conventional solid-state imaging apparatus, for example, it is known to read out an analog electric signal converted from an incident light in each pixel on every other column of the pixels arranged in a matrix, that is, the so-called horizontal skipped readout (having the same meaning as a horizontal thinning-out operation in the disclosure below), in the use of needing a high speed operation, such as a moving image.
Moreover, Japanese Patent Application Laid-Open No. 2006-025189 discloses the provision of an A/D conversion circuit to each column of pixels to perform the arithmetic processing of a digitized signal. To put it concretely, Japanese Patent Application Laid-Open No. 2006-025189 describes an image sensor provided with two register circuits per pixel column to store two different signal levels in the same pixel. After the storage, the image sensor operates the difference of the two signal levels in a digital region.
Moreover, solid-state imaging apparatus have required to have a wide dynamic range, and various techniques for the widening have been proposed. For example, Japanese Patent Application Laid-Open No. 2005-328493 discloses the configuration of providing an accumulation capacitor element for holding the charges overflowing from a photoelectric conversion element of each pixel. Besides the configuration, there is the technique of expanding a dynamic range on the basis of a signal based on a longer accumulation operation and a shorter accumulation operation.
If a horizontal thinning-out operation is performed in the circuit configuration disclosed in the aforesaid Japanese Patent Application Laid-Open No. 2006-025189 and an operation is performed on the basis of a signal held in each of the plurality of register circuits, then the A/D converters and register circuits in thinned-out, i.e., not read-out, columns become the state of not participating with the operation. The state admits of an examination in the aspect of the utilization efficiency of the circuits. Furthermore, the circuit configuration is required to expand the dynamic range thereof.